Phosphorus adsorption characteristics of soils and sediments surrounding Dishui Lake in Shanghai

Soils and sediments of different origins were collected, which included the cropland soils surrounding Dishui Lake, the sediments from rivers, the sediments of wetland and the sediments in Dishui Lake. These samples were used for the experiment of phosphorus isothermal adsorption. The results of this experiment were analyzed and fitted. It shows that, the adsorption-desorption equilibrium mass concentration (EPC₀ value) of the sediments in Dishui Lake (0.11-0.63 mg·L^-1) is higher than that of the soils and sediments from other sources, which indicates that it is easier to release phosphorus to overlying water. Both the Langmuir model and Freundlich model have a high fitting degree to the isothermal adsorption of phosphorus. The maximum adsorption capacity (Q_m) calculated by Langmuir model demonstrate that the adsorption capacity of soils and sediments from different sources follows the order: sediments from rivers (1003.05-2977.65 mg·kg^-1)>sediments in Dishui Lake (669.77-1717.94 mg·kg^-1)>sediments of wetland (368.60-1145.51 mg·kg^-1)>cropland soils (441.36-702.30 mg·kg^-1). It shows that the adsorption capacity of cropland soils is the weakest. Cropland soils can be a source of phosphorus in Dishui Lake when extra fertilizer is used.